Odd neck sizing scenario

[callgood]

.2505> .248 > .2465 .246 > .2455 .245 > .2450

I have some once fired Winchester .223 cases I want to size to .244. I measured them and the necks measured .2505 in diameter. I decided to take them down in stages to minimize stress on the necks, so I used a Redding titanium nitride bushing, ran 5 through, and measured them at .2465! I replaced the .248 with a .246 bushing, sized them again, .2455??? Used a .245 bushing, sized them again, finally .2455.

Has anyone ever experienced this? I am fairly new to rifle reloading and haven't read about this situation. How can a .248 bushing yield a .2465" neck?
I have 300 of these sized to .2465 at this point, but I don't want to make a career of neck sizing ("Yeah, old callgood, he shoots just so he can use his neck sizing die.)

But I'd still like to ease the brass down to .244. so I may omit the .246 and go directly to .244 from .246.

 

[USSR]

callgood,

Redding recommends necking down in steps of not more than .003 with their bushings for this very reason. Carry on as you have.

Don

 

[callgood]

Ahhhh, the Finger Lakes. Beautiful.

I went to the Redding site (which is where at some point I probably read about sizing down in steps) and this is what they said, 'tho they didn't really say why it happens. You can see the greatest over sizing occurs in the first step and diminishes as I get closer to .244. I could try going from .2465 to .244 in one step, the same reduction as the first step, and check to see if it sizes >.244. I'm thinking three steps will be required.

It has come to our attention through customer calls and our own use of the bushing style sizing dies that in certain instances, a given neck sizing bushing will produce a case neck diameter that can be several thousandths of an inch smaller than the actual diameter of the bushing. This idiosyncrasy occurs when the neck diameter of the fired case is a great deal larger than the diameter of the neck sizing bushing, such as occurs when factory chambers are on the large side of the tolerance range and the brass is on the thin side. Typically, we have not noticed any problems until the case neck is reduced more than 0.008-0.010".

Solutions include, increasing bushing diameter to compensate and/or the use of a size button. Reducing the neck diameter in two smaller steps by using an intermediate diameter bushing will also help. More concentric necks will also result using this method, as the case necks are stressed less during sizing. Don't forget to properly chamfer the inside and outside of the case mouths and apply a light coating of lubricant to the case necks before sizing